JPH0817400B2 - Optical signal distribution / selection device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical signal distribution / selection device using an optical transmission technique.

(Prior Art) In a system for processing a digitized video signal of a broadcasting station or the like, it is effective to introduce an optical transmission technique in order to realize high performance of the system because of high speed of a signal to be handled.
Currently, optical transmission is already being used for signal transmission in broadcasting stations. Further, it is considered that signal distribution selection is also performed by using optical technology.

Conventionally, as an optical signal distribution / selection device for this purpose, a device has been proposed in which a time division multiplexing technique and a wavelength multiplexing technique using a star coupler are used together. (A. Olipan
t) et al., “SMP TE Journal”, July 1987, pages 660-666).
This device will be described with reference to FIG. here
A device for 128 video signals will be described.

FIG. 3 (a) is a block diagram showing the overall configuration of a conventional optical signal distribution / selection device. This device comprises a plurality of local centers 2-1 ... 2-16 and a 16 × 16 star coupler 1
It consists of Different wavelengths are assigned to the transmission light sources of each local center, and the optical signal wavelength-multiplexed by the star coupler 1 is distributed to each local center. FIG. 3B is a diagram showing the configuration of each local center. In the transmitting section, eight digital image signals as inputs are multiplexed by the time division multiplexing circuit 12, and in addition to the electro-optical converters each having an output wavelength peculiar to each local center, the optical signals are star-coupled via the optical fiber. 1
Output to. On the other hand, the optical signal wavelength-division-multiplexed by the star coupler is transmitted to the optical receiving section of each local center by the optical fiber, first demultiplexed by the wavelength demultiplexing circuit 5, and then the photoelectric converter 6 for each wavelength. It is converted into an electric signal by -1 ... 6-16. Depending on the signal from the control signal generator 10, the 16 × 8 electrical matrix switch 8 can select 8 from 16 signals.
The signals are selected, and further, one signal is selected from the signals time-division-multiplexed by the time-division demultiplexing circuits 9-1 ... 9-8. By switching the connection state of the 16 × 8 electric matrix switch 8 and the time division separation circuits 9-1 ... 9-8, a plurality of signals can be freely extracted in any combination.

(Problems to be Solved by the Invention) In the optical receiver of the optical signal distribution / selection device described with reference to FIG. 3, the time-division-multiplexed and wavelength-division-multiplexed optical signals from a plurality of optical transmitters are switched and received. To do. At this time, if the time slots and the frames of the signals from the optical transmitters are not synchronized in time, there is a problem that the signals are out of synchronization when the signals are switched. If the optical receiver of each optical receiver has a phase synchronization pull-in circuit, all signals can be received, but there is a problem in that the device becomes complicated and the price becomes high. Further, even when the phase-locked pull-in circuit is used, there is a problem that a signal cannot be received immediately after the switching until the pull-in is completed. The purpose of the present invention is to
An object of the present invention is to provide an optical signal distribution / selection device that can realize time synchronization of the entire device with a simple configuration except the above-mentioned problems and that does not change the synchronization condition when switching signals.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the optical signal distribution / selection device according to the present invention has a plurality of optical transmitters and optical receivers each having an output wavelength different from each other. The local center and the star coupler to which the optical signals from the optical transmitters of the plurality of local centers are input and whose output end is connected to the optical receiver of the local center are included. The optical transmitter / receiver unit of the first local center generates a clock and a frame synchronization signal for the entire device to operate in synchronization therewith, and a unique unit assigned to the first local center for the clock and the frame signal. Each of the optical transmitters of the remaining plurality of local centers other than the first local center is connected to the input optical converter. A first time-division multiplexing circuit for multiplexing a plurality of electric signals, and an electro-optical converting means for converting an electric output of the time-division multiplexing circuit into an optical signal of a unique wavelength assigned to each local center. Optical receivers of all local centers including the local center of the above, clock signal generation means for converting the clock and frame synchronization signals transmitted as optical signals from the first local center into electrical signals, and an input wavelength multiplexed signal. Based on the output signal of the signal selection / photoelectric conversion means for selecting a plurality of signals of arbitrary wavelengths and timeslots in an arbitrary combination in accordance with the control signal and outputting them as electric signals, based on the output signal of the clock signal generation means. , For each local center, the time division multiplexing circuit, electrical conversion means, and means for controlling the operation timing of the signal selection / optical / electrical conversion means. It has a configuration which is characterized and.

(Operation) In the optical signal distribution / selection device according to the present invention, a signal transmitted from one of the optical transmission units of the plurality of local centers is
A clock and a frame synchronization signal that should be synchronized with the entire device were used. The other local centers operate the time division multiplexing circuit, the electro-optical converter, and the signal selecting / photoelectric converting means in synchronization with the clock and the frame synchronization signal generated by receiving the transmitted signal. As a result, the entire device is completely bit and frame synchronized. Therefore, even when switching signals,
The timing is never missed, and the time required for the phase synchronization pull-in is unnecessary. Further, in the present invention, a clock,
Since the frame synchronization signal itself is transmitted, the complicated electric circuit necessary for extracting the clock from the transmission signal is completely unnecessary.

(Embodiment) FIG. 1 is a block diagram for explaining the configuration of an optical signal distribution / selection device according to the present invention. Below, the clock,
The local center that sends the frame synchronization signal will be referred to as a main center for distinction. This embodiment comprises a main center 2-1a, local centers 2-2 ... 2-16 and one 16 × 16 star coupler 1. Eight-channel digital video signals are input to each local center. Here, the signal speed of each video signal is set to 150 Mb / s. Therefore, the signal speed of 8 time division multiplexing is 1.2 Gb /
It is s. Where star coupler and main center,
The lengths of the optical fibers connecting the local centers are all set equal when the device is installed. The length of one bit of the 1.2 Gb / s NRZ signal is about 0.8 nsec, and the optical fiber propagation delay time is ~ 5 nsec / m. Therefore, if the lengths are aligned on the order of cm, the phase shift of the signal does not matter.

FIG. 2A is a block diagram showing the configuration of the main center 2-1a. A clock serving as a reference for the entire apparatus and a part of the output of the frame synchronization signal generator 3 are added to the electro-optical converter 4 and sent to the star coupler 1 as an optical clock of wavelength λ1 and a frame synchronization signal. On the other hand, star coupler 1
Λ1 to λ16 wavelength multiplexed optical signal 1 × 16 wavelength demultiplexer 5
After being demultiplexed by each wavelength, the photoelectric converter 6-1 ...
It is converted to an electric signal at 6-16. Of these, the signal carried on the light of wavelength λ1 is the output signal of the clock / plane synchronization signal generation circuit 3, so the output from the opto-electric converter 16-1 is simply filtered and shaped by the clock generation circuit 7. The clock and the frame synchronization signal 7a are generated only by applying them. Based on this signal, the 16 × 8 electric matrix switch 8 and the 8 × 1 hour / minute separation circuits 9-1 ... 9-8 are operated in accordance with the channel selection control signal from the control circuit 10 to obtain an arbitrary combination. It is possible to extract eight 150Mb / s digital video signals.

FIG. 2B is a block diagram showing the configuration of a local center other than the main center. Since the structure and operation of the receiving unit are exactly the same as those of the main center, the description thereof is omitted here. The local center transmission unit will be described below. Eight 150 Mb / s digital video signals 11-1 ... 11-8, which are the inputs of the local center, are multiplexed by the time division multiplexing circuit 12 to become 1.2 Gb / s signals, and the respective electro-optical converters 4 are used to perform local It is sent to the star coupler 1 as a time division multiplexed optical signal of the wavelength assigned to the center.
At this time, the operations of the time division multiplexing circuit 12 and the electro-optical converter 4 are performed in synchronization with the clock and the frame synchronization signal output from the clock generation circuit 7.

As described above, the output of the clock generation circuit 7 is the reference clock sent from the main center 2-1a,
Since it is a frame synchronization signal, the opto-electric converter 6-1 is synchronized at the main center and each local center in synchronization with this signal.
6-16, time-division time-division demultiplexing circuit 9-1 ... 9-8, time-division multiplexing circuit 11-1 ... 11-8, and electro-optical converter 4 are operated to achieve complete synchronization of the entire apparatus. To be done. Therefore, even when the selection signal is switched, the device operates without any problem. Moreover, since the clock and the frame synchronization signal itself are sent from the main center, a complicated electric circuit for reproducing the clock from the video signal is completely unnecessary.

In the embodiment, the output of the opto-electric converter 6-1 is used in the main center, but naturally the output of the clock and the frame signal generation circuit 3 may be used. However, the photoelectric converter 6-
The use of the output of 1 has the advantage that the entire apparatus can be operated under the same synchronization condition as other local centers because the sending time by electro-optical, opto-electric conversion, and optical transmission is included.

(Effects of the Invention) As described above in detail, according to the present invention, an optical signal distribution / selection device that can realize time synchronization of the entire device with a simple configuration and that does not change the synchronization condition even when signals are switched is provided. It will be possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical signal distribution / selection device according to the present invention, and FIGS. 2 (a) and 2 (b) are block diagrams showing configurations of a main center and a local center used in the present invention,
FIGS. 3A and 3B are views for explaining a conventional optical signal distribution / selection device. In the figure, 1 is a star coupler, 2-1a is a main center, 2-1 ... 2-16 is a local center, 3 is a clock,
Frame sync signal generator, 4 is an electro-optical converter, 5 is a wavelength demultiplexer, 6-1 ... 6-16 is an opto-electric converter, 7 is a clock generation circuit, 7a is a clock, frame sync signal, 8 is electrical Matrix switches, 9-1 ... 9-8 are time division demultiplexing circuits, 10 is a control circuit, 11-1 ... 11-8 are electric signals, and 12 is a time division multiplexing circuit.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area H04B 9/00 T

Claims (1)

[Claims] 1. A plurality of local centers each having an optical transmitter having an output wavelength different from each other and an optical receiver, and optical signals from the optical transmitters of the plurality of local centers are input and output. An optical transmitter / receiver of a first local center of the plurality of local centers, the end of which is composed of a star coupler connected to an optical receiver of the local center, and a clock with which the entire apparatus operates in synchronization with it. A frame synchronizing signal generating means, and an electro-optical converting means for converting the clock and frame signals into an optical signal of a unique wavelength assigned to the first local center, and the rest other than the first local center. Each of the plurality of local center optical transmitters outputs a time-division multiplexing circuit that multiplexes a plurality of input electric signals and an electric output of the time-division multiplexing circuit, respectively. Optical-electric conversion means for converting into an optical signal of a unique wavelength assigned to the local center of the optical receiver, and the optical receivers of all the local centers including the first local center receive the optical signal from the first local center. A clock signal generating means for converting a clock transmitted as a signal and a frame synchronization signal into an electric signal, and a plurality of signals of arbitrary wavelengths and timeslots are selected from an input wavelength multiplexed signal in an arbitrary combination according to a control signal. Based on the output signal of the clock signal generation means and the signal selection / photoelectric conversion means for outputting as an electric signal by the time division multiplexing circuit, the electrooptic conversion means, the signal selection / photoelectric conversion. And a means for controlling the operation timing of the means.